One-way drive for propellers



Oct. 18 1938.

F. W. CALDWELL ONE-WAY DRivE F R PROPELLERS Filed A rii 2:5, 1936 4 Sheets-Sheet l INVEN TOR. EmKWLT'aHue/f A TTORNE Y I Oct. 18, 1938; F. w. CALDWELL. 2,133,655

ONE-WAY DRIVE FOR PROPELLERS Filed April 23, 1936 4 Sheets-Sheet 2 ATTORNEY I Oct. 18, 1938. F. w. CALDWELL ONE-WAY DRIVE Fofi PROPELLERS Filed April 23, 1936 4 Sheets-Sheet IN VEN TOR.

3Y7; z ft ATTORNEY Oct.. 18, 1938.

INVENTOR.

EMWZTaHme/Z ATTORNEY Patented Oct. 18, 1938 ONE-WAY DRIVE FOR PROPELLERS Frank W. Caldwell, Hartford, Conn., assil'nor to United Aircraft Corporation, East Hartford, Conn., a. corporation of Delaware Application April 23, 1936, Serial No. 76,036

1 Claim.

This invention relates to propeller drives and has particular reference to a one-way, or a free wheeling drive for a controllable pitch aeronautical propeller.

5 An object of the invention resides in the provision of a suitabe one-way drive between the propeller and the engine so that under certain circumstances the propeller may rotate freely with respect to the engine, and the pitch of the 10 propeller blades may be maintained at 'a value such that the propeller will offer the minimum resistance to the progress of- -the airplane upon which it is mounted, or; in other words, will give the minimum drag during such free rotation.

15 A further object resides in the provision between a controllable pitch propeller and the propeller driving engine of a drive eiiective to trans- 30 parts throughout, there is illustrated a suitable mechanical embodiment of one form of the idea of the invention; The drawings, however, are for the purpose oi illustration only and are not to be taken as limiting the invention.

5 In the drawings, Fig. 1 is an elevational view of a fragmentaryportion of an engine, a propeller and a propeller drive constructed according to the idea of this invention, certain portions being broken away and shown in section to better illus- 40 trate the construction thereof. This figure also includes a fragmentary illustration of a suitable manually adjustable governor for controlling the controllable pitch propeller.

Fig. 2 is a sectional view on the line 22 of Fig. 1.

Fig. 3 is a fragmentary perspective view of certain portions of the propeller particularly illustrating one of the counterweights illustrated in 50 Fig. 1, and the limit stop mechanism included in the counterweight for determining the range of pitch change of the propeller blades.

Fig. 4 is a view similar to Fig. 1 showing a somewhat modified form of the device or the in- 55 vention.

Fig. 5 is a sectional view on the line 5-'-5 of Fig. 4. I

Referring to the drawings in detail, the numeral I generally indicates a suitable propeller driving engine which may be a radial air-cooled internal combustion engine frequently employd for the propulsion of airplanes, but may be any other suitable propeller drive power plant without in any way exceeding the scope of the invention. The engine illustrated is provided with a nose section l2 through which extends an engine drive shaft I i. The drive shaft I4 is tubular in construction and is supported in the nose piece l2 by an anti-friction bearing I Gwhich centers the shaft with respect to the nose piece and also transfers the propeller thrust to the engine and the airplane upon which the engine is mounted.

Forwardly of the nose section l2 the drive shaft it is provided with a cylindrical portion l8 upon which is mounted the controllable pitch propeller 29 generally indicated at 20, the propeller being supported upon and centered with respect to the drive shaft by means of a pair of spaced apart anti-friction bearings 22 and 24.

'lne propeller blades 25 are secured upon a 25 propeller hub portion or spider member '28 by means of a two-part barrel member in such a manner that the blades are rotatably mounted upon the respective radially extending 'arms 32 of the hub portion. Thus the blades may be 31 rotated about their respective longitudinal axes to change the pitch angle of the blades.

A suitable hydraulic mechanism is provided for moving the blades in one direction of pitch angle adjustment'and suitable centrifugally actuated 35 means are provided for moving the blades in the cpposite direction. In the hydraulic pitch changing mechanism illustrated, a relatively fixed piston 34 is mounted upon the forward end-of the hub member 28 by suitable cooperating screw 40 threads 38 and carries upon the exterior thereof a reciprocable cylinder 38, the rearward endof which is operatively connected with the counterweights 40 by means of a suitable cam and pin connection particularly illustrated in Fig. 3, the earn being designated by the numeral 42 and the pin by the numeral M. The counterweights lilare mounted upon outwardly extending counterweight arms it which are non-rotatably securedto the root ends of the blades 26 by means of so integral ring portions 48 and vernier pin connections '50. In the form of propeller illustrated, the ring portion 48 is connected to a sleeve member 52 which is non-rotatably secured within the hollow base or root portion. of the pro- 5 the tubular drive shaft.

peller blade. A suitable hydraulic seal 54 is provided between the outer end of the piston member 84, and the head 56 of the cylinder so that the introduction of fiuid under pressure into the space between the forward end of the piston and the cylinder head will cause an outward movement of the cylinder which will be transferred to the counterweights 48 through the pin and cam connections between the cylinder and the counterweights and will be transmitted to the propeller blades by the counterweight arms 48 and pin connections 58. Upon a decrease in the pressure of the fluid between the piston 34 and cylinder 56, the counterweights 48 will move under the actuation of centrifugal force to rotate the propeller blades 26 and at the same time move the cylinder 38 toward its rearward position illustrated in Fig. 1. In one suitable form of propeller, the counterweights 48 are used to move the blades toward their high pitch condition and the cylinder 38 is used to overcome the action of the 'counterweights and move the blades toward their low pitch condition. The hydraulic fluid under pressure is supplied to the space between the forward end of the piston 34 and the cylinder head 56 through a tubular extension 88 mounted within the tubular forward end of the drive shaft I4 and secured at its rear end in a plug member 68 rigidly secured in the bore of The hydraulic fluid is supplied from some suitable pressure source such as a pump and is fed through the manually ad-.

justabie speed controlling governor 62 and a conduit 84 leading from the governor to the interior of the plug 68, through a suitable oil collector ring 68 positioned between the rotatable drive shaft and a fixed portion 68 of the engine.

Referring to Fig. 3, it will be observed that each counterweight is provided with limit stops for determining the position of the propeller -blades at each end of the range of pitch adjusting movement of the blades; In the form of propeller illustrated, a fiat anti-friction bearing I8 'is disposed between the pin 44 and the counterweight 48, one race of this bearing comprising a disc shaped member 12 fixed upon the pin 44 adjacent to the end thereof remote from thecylinder 38. Above the disc 14, the pin is provided with an upward extension 16. The counterweight is provided with a longitudinal slot or trough I8 within which there is disposed a cylindrical member 88 provided with external screw threads adjacent its ends and provided intermediate its length with a transverse pin 82 which extends into suitable extensions 84 of the trough I8 to secure the cylindrical member against rotation and longitudinal movement with respect to the counterweight. A nut 88 is screw threaded upon one end of the cylindrical member 88- and a similar nut 88 is screw threaded upon the opposite end thereof, both nuts 86 and 88 being maintained in adjusted position upon the cylindrical member by contact of their'sides with the sides of the trough I8 and being so positioned that the extension 16 upon the pin 44 will come in contact with a respective one of the nuts 88 and 88 at each end of the range of movement of the respective propeller blades. Thus, by reason of the contact of the extension 18 with the limit stop nuts 88 and 88, the range of pitch changing movement of the. propeller blades may be definitely selected and limited. For ordinary operation this range will fall somewhere within the range of pitch changing movement extending from approximately five degrees to approximately fifty degrees.

a saese At its forward end the propeller hub member 28 is supported directly upon the outer race of the anti-friction bearing 22, but at its rearward end it is supported upon a cylindrical sleeve-like extension of an inner member 88 of a one-way clutch generally indicated at 82, the clutch member 98 being in turn supported upon the outer race of the anti-friction bearing 24. The outer member 94 of the one-way clutch is operatively secured upon the drive shaft l4 by means of suitable splines 98 which engage with similar external splines 88 provided upon the drive shaft immediately forwardly of the anti-friction bearing I8.

The propeller is definitely located upon the drive shaft I4 by means of a nut I88 which clamps the inner race of the anti-friction bearing 24 against a radial annular shoulder provided. on the drive shaft and a nut I82 which bears against the inner race of the anti-friction bearing 22, the outer race of which bears against a suitable annular shoulder I84 provided within the hub portion 28 of the propeller, the rear end of the propeller hub member bearing against the inner clutch-member 88 as indicated'at I84, and the clutch member in turn bearing against the outer race of the anti-friction bearing 24. Also the outer race of the bearing 22 is fixed within the hub portion and restrained against movement in either direction by reason of the fact that the rearward end of the piston 34 which, as explained above is screw threaded into the forward end of the hub member, bears againstthe forward side of the outer race and clamps it rigidly against the annular shoulder I84. An additional restraint against axial movement of the propeller and drive shaft with respect to the engine is obtained by permitting the outer race of the anti-friction bearing 24 to bear against the forward side of the outer clutch member 84 and permitting the rearward side of this outer clutch member to bear against the forward side-of the inner race of the main roller bearing Hi.

The outer one-way clutch member 84 is provided with a forwardly extending annular portion. I88 which overlies a corresponding annular portion I88 of the inner clutch member 88. A plurality of rollers H8 are disposed between these two annular portions and located in suiteble depressions provided in the periphery of the inner clutch member to provide a one-way or free wheeling drive between the outer and irmer clutch members as particularly ilustrated in Fig. 2.

In the form of one-way clutch illustrated in Fig. 2, each of the rollers I I8 is received in an individual depression H2 provided in the periphery of the inner clutch member 98. -The bottom of each of the depressions I I2 is sloped upwardly from a tangent to the arc of the medial depth of the depressions so that as the rollers move in the depressions in a counterclockwise direction as indicated in Fig. 2, they will become tightly wedged between the bottoms of the depressions and the inner surface of the overlying annular portion I 88 of the outer clutch member 84 and will in this condition provide a driving connection between the outer and inner clutch members. If, however, due to a change in the speed of the outer clutch member, the inner clutch member tends to drive the outer clutch member, the rollers will be moved backwardly into the deep ends of the depressions I I2 and the driving connection between the two clutch members will be broken so that the inner clutch member may rotate freely with respect to the outer clutch member in the same direction of rotation at a greater speed. One or more coiled compression springs II4 are provided in connection with each of the rollers IIII to resiliently urge the rollers toward the shallow end of the respective depressions so that a driving connection will be made as soon as the outer clutch member tends to drive the inner clutch member.

A suitable oil seal H6 is provided between the coextensive annular portions of theinner and outer clutch members and oil is fed to the clutch through a channel I I1 inthe plug 60 and from.

the shaft l4 through suitable channels II8, the annular channel I20, and the anti-friction bearing 24, an annular space I22 being provided between the sleeve portion of the inner clutch member 80, and the exterior of the cylindrical portion I6 of the drive shaft to the anti-friction bearing 22. I

Referring now to themodifled form illustrated in Figures 4 and 5, the drive shaft I24 is provided with a long tubular extension extending beyond the front side of the propeller. In this form of the invention the propeller hub member I28 is provided upon each side of the propeller supporting arms I32 with relatively long cylindrical extensions, the forward extension being indicated at I34 and the rearward extension being indicated at I36. The elongated hub member I28 is concentric with, and overlies the major portion of the length of the forward extension of the crankshaft, and bearings I38 are interposed between the outer surface of the drive shaft and the inner surface of the elongated hub member. At its rearward end-the rear extension I36 of the hub member is received in the forward end of the fixed nose portion 12 of the engine and is supported therein by a pair of spaced apart antifriction bearings I40 and I42, the bearing I40 being the usual centering and propeller thrust load carrying ball bearing and the bearing I44 being a roller bearing provided to assist in center ing the propeller carrying hub I28 and also to support at least a portion of the propeller weight in cantilever reaction. The two bearings I40 and I42 are mounted in a cage I44 which is secured in the nose section I2 by means of the bearing cover I46 secured in place by the bolts 8. R'I'he bolts I48 also secure to the nose portion. a fixed sleeve member I50 which surrounds the forward end of the drive shaft within the nose portion and forms a part of a suitable speed reduction gear, not illustrated, between the engine drive shaft and the propeller shaft I24. This fixed member I66 receives the lower end of the hydraulic fluid conduit 64 and within the portion of the fixed member which receives the oil conduit, the propeller shaft is provided with a radial extension I62 which bears against the inner surface of the sleeve member I50 and is provided with oil seal rings I64. An oil conduit I56 leadsfrom between the rings I64 to the interior of the hollow propeller shaft I24 and a plug I58 is provided in the erally indicated at I64.

propeller shaft immediately rearwardly of the inner end of the conduit I66 so that provision is made for introducing hydraulic fluid under pressure from the manually adjustable governor 62 to the interior of the drive" shaft I24.

At its forward end the forward extension I 34 with an outer annular portion I66. This outer annular ,portion is provided with an oil seal I68 which bears against the inner surface of a cylinder I reciprocably mounted upon the member I62 and operatively connected with the counterweights 44 by pin and cam connections as illustrated in Fig. 3. The splines I60 are tapered and the member I 62 is rigidly secured thereon by a nut I12 screw threaded upon the forward end of the extension I34, a packing I14 being interposed between the nut and the member I62 to prevent hydraulic fluid from leaking past the member I62 and flowing along the forward extension I34 of the hub member.

The drive shaft I24 is provided at its forward end with tapered external splines I16 and upon these splines there is rigidly mounted the inner member I18 of the one-way clutch I64, the member being rigidly secured upon the tapered splines by means of a nut I80 screw threaded upon the extreme forward end of the drive shaft. An oil seal M32 is provided between the nut I80 and the member 618 to prevent the leakage of hydraulic fluid between the member I18 and the shaft I24.

Oil leaking through the clutch and into the space between the forward end of the extension I34 and the forward end of the shaft I24 is stopped by the forward bearing I38 between the drive shaft and the hub member. The piston is provided with a head I83 which forms a chamber between its inner surface and the members I62 and I18, into which hydraulic fluid may be introduced through the tubular drive shaft to cause the cylinder I10 to reciprocate and move the counterweight 40 to rotate the propeller blades 26 to various pitch angle positions.

The annular portion I66 of the outer clutch member I62 overlies the inner clutch member I18 and a plurality of clutch rollers I86 are disposed between the outer and inner clutch members. As particularly illustrated in Fig. 5, each of the rollers i86 is located in a cam shaped depression I88 provided in the periphery of the inner clutch member I18 and each roller is urged toward the shallow portion of the cam depression by one or more coiled compression springs I 90.

With the above described modified construction, power is transmitted through the elongated drive shaft I24 to the inner clutch member I18 to rotate the same. When the inner member I18 rotates at a speed sufficient to transmit power from the inner member to the outer member I62, the rollers are moved out of the deeper portions -of the depressions I88 and cammed between the bottoms of the depressions and the interior surface of the annular portion I66 of the outer gluten member I62 so that adrive is provided through the one-way clutch from the drive shaft I24 to the forward extension I34 of the propeller hub member I28 and from this hub member to the other elements of the propeller. The long tubular shaft I24 and the forward extension I34 on the propeller hub member provide a flexible resilient drive between the engine and the propeller which tends to damp out a large portion of the engine vibrations before they are transmitted to the propeller and the one way clutch I I64 provides a drive whereby the engine will drive the propeller in one direction of rotation and the propeller is free to overrun the engine in the same direction of rotation at a speed greater than the rotatibnal speed of the drive shaft I24.

The automatic one-way drive provided between the engine and the propeller in the 'two modifications illustrated in the accompanyin drawings,

and described above, may be utilized to serve two different purposes. The preliminary purpose of the device is for use on the engines of multimotored aircraft. Most airplanes provided with a number of motors are able to maintain themselves in flight with less than the total number of motors provided and it at times becomes desirable to stop at least one of the motors. It may be that the total number of motors is provided for take-off and climb with load, and that when the airplane has reached its cruising altitude and leveled off at cruising speed, eilicient operation may be achieved by stopping one or more of the motors and proceeding with only a part of the total number of motors in operation. It occasionally happens that one of the motors of the multi-motored airplane may fail in service, and thereby render it necessary to proceed with the remaining motors carrying the defective motor as a dead'motor. In either case it is highly desirable that the drag of the dead motor be reduced to a minimum, and as the only alterable drag factor is the propeller drag, it becomes desirable to provide some means to achieve a propeller condition consistent with minimum negative thrust or drag..

One means which has been proposed foraccomplishing this purpose is to feather the propeller blades, that is, turn the blades to such a pitch angle condition that the width of the blades is substantially parallel to the direction of motion. This condition, however, involves a great many difficulties, and a considerable amount of additional hazard, as it has been found that it is not always feasible to move the propeller blades through such a wide range of pitch angle adjustment as to' bring the blades into and out of a feathered condition. Even disregarding the element of hazard, a very large, heavy, and expensive mechanism is necessary to move the blades through such a large angular range. It has been found that the same condition, and in many cases an even better condition of minimum resistance may be obtained by allowing the propeller to rotate freely in a condition of relatively high pitch, which is, however, not anywhere near a feathered condition. Thus in most instances a minimum drag condition can be obtained by allowing the propeller to free wheel at a pitch angle of some thirty to fifty degrees, in which case the negative thrust or drag of the propeller on the dead engine becomes practically negligible.

The other purpose which may be served by the invention is that of using the propeller as a brake to slow down the speed of an airplane during landing or maneuvers involving long dives. In this case the'invention would apply to a single engine as well as to a multi-engine airplane. It has been found that the drag or negative thrust of the propeller can be greatly increased by allowing the propeller to rotate freely ata relatively low pitch angle, the drag in some cases becoming substantially equivalent to that of the area of the entire propeller disc.

In the present invention a controllable pitch propeller is provided having adjustable limit stops as described above which are desirably set to limit the pitch angle of the propeller at the most advantageous value for one or the other, or both, of the above purposes. Thus each of the counterweights 40 is provided with two limit stops, one of which may be set to maintain the propeller at its most advantageous low pitch angle for braking purposes and the other of which may be set to maintain the propeller at its most advantageous high pitch angle for reducing the propeller drag. In case of engine failure with a consequent loss of pressure of the hydraulic fluid supplied to the propeller operating cylinder, the counterweights would automatically carry the propeller blades to their high pitch condition as ascertained by the upper limit stop and as the engine slowed down and stopped the propeller would continue rotating freely about the propeller shaft. Thus the drag of the propeller would, be reduced to its minimum value and at the same time the propeller would be drivingly released from the engine-so that it would not tend to continue rotating the engine with the danger of destruction of the engine in case of some mechanical failure. When theengine is slowed down for landing or for a dive, the pressure on the hydraulic fluid is maintained and under these conditions the pilot can control the speed governor so that the propeller is forced into and maintained in its low pitch condition. With the engine thus slowed down the propeller will rotate relative to the engine under the influence of aerodynamic forces due to the forward speed of the airplane, and if it is held in the flat. or low pitch condition mentioned will serve as an effective brake to prevent excessive speed of the airplane during the landing glide or dive.

In any case the limit stops will be so positioned that when the propeller is free wheeling in either one of its limit conditions, that is either in positive high pitch, or positive low pitch, the pitch angle as determined by the limit stops will be out of the range of pitch angles which would give to the propeller an excessive rotational or dangerous tip speed while it is rotating freely under the influence of aerodynamic forces.

While there has been illustrated and described a suitable mechanical embodiment of what is now considered to be the preferred form of the idea of the invention and one modification thereof, it is to be understood that the invention is not limited to the particular mechanical embodiment so illustrated and described, but that such changes in the size, shape, and arrangement of parts may be resorted to as come within the scope of "the appended claim.

Having now described the invention so that others skilled in the art may clearly understand the same, what it is desired to secure by Letters Patent is as follows:

What is claimed is:

In a drive for a controllable pitch aeronautical propeller provided with hydraulically actuated means comprising a piston and cylinder device propeller may rotate freely with respect to the propeller driving engine under the influence of aerodynamic forces whenever the speed of the engine falls below the speed imparted to said propeller by said aerodynamic forces, said piston comprising two concentric parts constituting an inner and an outer ring for said one-way drive, radial cams in at least one of said rings, and looking rollers between said rings.

FRANK W. CALDWELL. 

